Automatic devices for transcutaneous biopsy have heretofore been provided, which use suitable needles for sampling tissues.
In particular, the biopsy needles usually include a cannula that has a sharp edge at its distal end.
A rod or stylet with a suitably pointed distal end is slidably inserted into the cannula. The pointed end of the stylet goes out of the cannula when the first is wholly inserted in the latter.
At its pointed distal end, the stylet features also a longitudinal cavity for receiving a bioptic sample of tissue to be examined.
The needle is usually used during the patient's complete anesthesia and under control of radiographic and ultrasonographic monitoring and visualization means.
The needle is introduced through the skin until the pointed distal end, protruding from the cannula, partially penetrates the tissue to be analyzed.
Then, the stylet is moved quickly forward for a predetermined length, to introduce the above mentioned cavity into the tissue.
Afterwards, the outer cannula is moved quickly forward, so that the sharp edge thereof cuts the portion of tissue contained in the cavity of the stylet like a guillotine; the portion of the tissue thus obtained is closed and kept in the cavity of the stylet.
Then, the needle is withdrawn and the bioptic sample is removed.
Automatic biopsy devices currently used, have a moving element which slides within a box-like covering and supports the cannula and the stylet of the needle, which are subjected to elastic reaction, usually created by related springs.
The springs, previously loaded and operated by a suitable push button, allow the stylet and the cannula to move quickly forward in a proper order.
In practice, the above described devices can automatically carry out a first working step, in which the stylet moves forward and its distal end is uncovered by withdrawing a predetermined portion of the stylet from the cannula, and a second working step, in which the cannula cuts the portion of the tissue contained between the stylet cavity and the inner wall of the cannula, while the cannula slides on the stylet, until the cavity of the stylet is wholly covered.
In the step in which the device is loaded, the cavity of the stylet is inside the cannula. During the loading step, a safety catch is possibly automatically inserted to avoid incidental operation of the device, and then the springs are loaded to expel the needle later on.
During the needle ejection, after the safety catch has been removed and the needle has been introduced into the organ to be examined, the operation button is pressed, so as to move forward first the stylet and then the cannula, due to the unloading action of the springs on respective moving elements, as described above.
Reported disadvantages of above described devices derive from irksome and difficult loading of the springs. The springs are loaded by e.g. mutual rotation of two portions of the box-like covering, by means of a kinetic mechanism for loading the springs activated by a series of helical guides, or by axial sliding of a suitable cursor.
In any case, loading of the springs involves the operator's both hands and requires a considerable effort, due to the resistance of the springs, which must have considerable elastic force for the subsequent needle ejection step.
Moreover, the springs loading mechanisms are often complicated and their use is difficult, because the operator must take practice of all the necessary operations and needs a fairly good specific manual ability.
Another drawback of the known needle devices lies in the fact that also the introduction of the needle requires a quite big number of operations, because e.g. a lid of the box-like covering must be previously opened.